Hydraulic support for the movably supported roller in roll presses

ABSTRACT

A hydraulic support for the movably supported roller in roll presses in which the hydraulic circuit includes a motor pump, a maximum-minimum pressure switch and a safety valve. The circuit further includes a pressure-limiting valve set for an operational pressure corresponding to a predetermined pressing force in the roller gap and slightly higher than the minimum pressure at which the maximum-minimum pressure switch is set. The operational pressure in the support may thus be kept constant notwithstanding fluctuations in the load pressure.

United States Patent 1 Bergendahl [451 May 27, 1975 HYDRAULIC SUPPORT FOR THE MOVABLY SUPPORTED ROLLER IN ROLL PRESSES [76] Inventor: Hans-Georg Bergendahl,

Nevelstrasse 32, 463 Bochum, Germany 22 Filed: Feb. 6, 1974 21 Appl. No.: 439,888

[30] Foreign Application Priority Data Feb. 6, 1973 Germany 2305685 [52] US. Cl. 100/47; 100/170; 72/20; 72/21; 241/231 [51] Int. Cl B30b 15/16; B30b 3/04 [58] Field of Search 100/168, 169, 170, 4751; 72/20, 21; 241/230, 231

3,075,417 1/1963 Blain 72/20 3,555,596 1/1971 Thieme 100/170 X FOREIGN PATENTS OR APPLICATIONS 377,616 7/1932 United Kingdom 241/231 796,039 6/1958 United Kingdom 241/231 Primary Examiner Peter Feldman Attorney, Agent, or Firm-Salter & Michaelson [57] ABSTRACT [56] References Ci d thus be kept constant notwithstanding fluctuations in UNITED STATES PATENTS the load Pressure- 3,024,679 3/1962 Fox 100 170 ux 3 C a m 2 awing Figures #H% 1a '20 F I 8 l I I 26- j s f l 7 I l 3 24 Z2 Z0 4 PATENTEUrcAY 27 m5 HYDRAULIC SUPPORT FOR THE MOVABLY SUPPORTED ROLLER [N ROLL IRESSES FIELD OF THE INVIZN'IION The present invention relates to a hydraulic support for the bearing blocks of a movable. supported roller in roll presses with at least one hydraulic cylinder for each bearing block mounted between the press frame and that side of the bearing block which is away from the roller gap. and more particularly to such a hydraulic support which is supplied from a motor pump and wherein a maximum-minimum pressure switch is connected in parallel to the hydraulic cylinder and where furthermore a hydraulic accumulator for storage and a safety valve are located. and further including means in the hydraulic circuit to automatically maintain the operating pressure notwithstanding fluctuations in load pressure.

BACKGROUND OF THE INVENTION Hydraulic supports ofthe kind mentioned are used in roll presses for pressing briquettes and also in compacting presses as overload safety devices in order to prevent rupturing the press. as if. for instance, an alien body should happen between the rollers together with the briquettes or the material being compacted Ifsuch an alien body finds its way into the roller gap. the safety valve will respond, being normally set for a pressure l5 to 20?! above that which occurs in the hydraulic circuit for normal operation of the press. The oil expelled from the hydraulic cylinders in normal operation when pressure fluctuations and pressure pulses are encountered will be absorbed in the hydraulic storage because only minor shifts of the bearing blocks will occur in normal operation. lvlaintaining an essentially constant pressure will be achieved by one hydraulic storage of relatively small storage volume. A maximum-minimum pressure switch controls the drive motor of the pump. Ordinarily. the hydraulic circuit of the hydraulic support may be connected to the tank by means of a shut-off valve. The system pressure may be eliminated by means of this shut off valve. A special hydraulic support is provided for each of the two bearings of the axially movable. supported roller in a roll press. Both hydrauhe supports may be supplied from the same pump.

As regards known roll presses. overloading of the press due to overfilling of the roll gap by the material to be compacted will be avoided by controlling the supply of the material to be compacted as a function of the pressure loading. Such control may take place furthermore as a function of motor load or also as a function of the bearing load. or again as a function of the stresses in the press structure.

As regards compacting presses which operate with rollers provided with smooth roller shells. a special problem arises because the press must be started with as small as possible a roller gap-vvidth. so as to initiate formation of the material-shell. Ordinarily. one starts with a gap width of 0.5 to l nnn. The material to be compacted which predominantly is highly fluid will be applied at this gap width. After a material shell has been formed by the initial gap width. increasingly more material will be grasped by the rollers. 'lhereby the rollers will be pressed apart until finally the material-shell will be of the desired thickness. 'l'his thickness may amount to It! to [5 mm. The roller gap is increasingly wide in normal operation. \ariation of the roller gap from initial position when starting to the operational position may be as much as 2U007t. Thereby. an appreciable increase in pressure will occur in the hydraulic support, which may no longer be economically absorbed by a hydraulic storage. On the other hand. precisely when starting a press. maintaining the predetermined operational pressure is critical and to date. this problem has been met manually letting out as much oil through the shut-off valve. wlhile observing the manometer that an approximately constant pressure is being obtained. Obviously. such manual control of the operational pressure will only be feasible in exceptional cases when starting a press. Difficulties therefore will be unavoidable when there are fluctuations in material sup ply or when such are interrupted. In these cases then. the same manipulations must be carried out as when starting the press. Therefore, it is necessary to tie down an operator for observing and operating such a press.

SUMMARY OF THE INVENTION The object of the invention is the creation of means allowing automatic starting of compacting presses and also automatically meeting fluctuations and interruptions in material supply. so that steady monitoring of the press on the part of an operator will become superfluous.

The problem of hydraulic supports of the abovementioned kind relating to presses will be solved by the present invention in that a pressure-limiting valve set to operational pressure would be connected to the hydraulic circuit. In order to maintain as constant as possible an operational pressure in the press. the connection between the hydraulic cylinders and the pressurelimiting valve should be as low as feasible in losses and. furthermore. the pressure-limiting valve should be so designed that there will be as low loss as possible under the given conditions. In practical terms. this means that the hydraulic cylinders are connected to the pressurelimiting valve by means of lines as short as possible and as large in cross section as possible.

The invention is illustratively shown in the drawing and described in detail below in relation to that drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. I shows schematically a side view of a roller press with a hydraulic support in conformity with the present inventionv FIG. 2 shows the hydraulic circuit arrangement of the hydraulic support of the present invention.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS In the roll press shown in FIG. 1. two press rollers 4 and 6 are mounted next to each other in a press frame 2. These press rollers are supported in bearing blocks 8 and I0 which are mounted in lateral openings 12 of the press frame. Bearing blocks 8 of roller 4 are stationary. whereas bearing blocks 10 of roller 6 may be moved between parallel guiding surfaces of the frame opening 12. A spacer I4 is mounted between the hearing blocks. Bearing block III abuts a hydraulic support 1b. which in every case is provided with a cylinder block l8 with two cylinder boreholes each holding one support-piston 20. One line 22 each is connected to each of the cylinder bore holes said lines 22 belonging to a hydraulic circuit connected to a tank 26 via a pres- 3 sure-limiting valve 24 and into which hydraulic circuit oil under pressure is fed in by a motor-driven pump 28. A hydraulic storage tank 30 and a maximum-minimum pressure switch 32 are connected to the hydraulic circuit.

The circuit of the hydraulic support is shown in a larger scale in FIG. 2. Pump 28 conveys oil from tank 26 via a back-pressure valve 34 into a line 36, to which are connected the maximum-minimum pressure switch 32 and the hydraulic storage tank 30. Furthermore, cyl inder chamber 38, of the hydraulic drive. with pistons 20 are connected to said line, said pistons 20 being located in the cylinder block 18. Furthermore, a pressure-limiting valve 24 is connected to line 36, said pressure limiting valve also being connected by means of a return-oil line 40 to tank 26. A shut-off valve 42 is appropriately provided as a further connection to the tank, emptying of the hydraulic circuit being feasible through said valve 42. As is the ease for the known hydraulic supports, such a hydraulic circuit is provided for each of the bearing blocks of the axially movable roller, as indicated in FlG. 2 by line 36' and the backpressure valve 34 associated with said circuit.

The pressure-limiting valve 24 is set for a pressure corresponding to the desired pressing pressure in the roller gap. The switch-on pressure of the maximumminimum pressure switch 32 will be set somewhat lower than that pressure for which the pressure-limiting valve 24 itself is set. When starting the press, press rollers 4 and 6 will be in the position of the narrowest roll gap. This position will be given by spacer 14. The roll gap amounts to 0.5 to 1 mm. The material to be compacted will be supplied to the rollers by means of the supply chute 44. This material will be grasped by the rollers which at first will form a thickness corresponding to one shell. The moment there is shell formation the rollers will continuously draw in more material. Because the shell will increase in thickness. roller 6 will be moved away from roller 4. This will simultaneously increase the real pressure in the hydraulic circuit ofthe hydraulic support. Because the overflow valve 24 is set for operational pressure, which is only slightly above the system pressure set by the maximum-minimum pressure switch 32, the operational pressure of the movable roller 6 will be kept constant by means of pressure-limiting valve 24 over the entire adjusting range of the moving roller 6. This means however. that the shell will already be generated at constant press pressure during the start of the press and also that during further operation of the press. the predetermined press pressure will be kept very accurately. Hydraulic storage tank 30 being prc-biased with the system pressure, there will be no discharging of this storage when the pressure-limiting valve 24 responds. In order to maintain a constant pressing force, the connection between cylindcr chambers 38 and pressure-limiting valve 24 should be as low-loss as possible. Appropriately, lines establishing this connection should be of as little flow-resistance as possible. that is. they should be of the largest possible crosssection and as short as possible.

If the material supplied should be interrupted during operation. the oil under pressure in the hydraulic storage tank 30 will be released into the hydraulic circuit. This initiates the return setting motion of the movable roller in direction of the stationary one. The moment the pressure has fallen below the minimum pressure set bl l at switch 32, pump 28 will be switched on and oil under pressure will be supplied until that system pressure again is obtained. by means of which roller 6 will be brought into its end position, from which the shellformation will be initiated again when material supply resumes.

lf merely a reduction in material supply should occur during operation, a feed adjustment for the movable roller in the sense of a narrowing of the roller gap will be initiated in the same manner by means of the hydraulic support, so that, in this instance too, first, oil under pressure stored in storage tank 30 will be supplied and then. afterwards, the final adjustment will occur with respect to pump conveying. If the material supply is then increased again, release of oil under pressure through the pressure-limiting valve 24 will again achieve constant press pressure.

In order to initiate with as little delay as possible the feed adjustment of roller 6, the pressure storage 30 should be connected in as low-loss a manner as possible with a cylinder chamber 38. The difference between the pump switch-off pressure set at the maximumminimum pressure switch 32 and the predetermined operational pressure obtained from the setting of the pressure-limiting valve 24 should be as small as possible. The minimum of said pressure difference is determined on one hand by the response tolerances of the pressure-limiting valve 24 and on the other by those of pressure switch 32.

The hydraulic circuit furthermore can be made safe by a convcntiotutl safety valve which would be actuated in case of failure of the pressure-limiting valve 24.

As regards the terminology of the oil circuits in hy draulic drives, operation ofthe hydraulic support of the invention may be designated as operation with open oil circuits. in contrast to known hydraulic supports, of which the operation then would be designated as closed oil circuits.

It will be obvious to those skilled in the art that various changes may be made without departing from the scope of the invention and the invention is not to be considered limited to what is described in the specification.

What is claimed is:

l. A hydraulic support for the bearing blocks of a movable roller in a roll press having a frame and two rollers having a gap thcrebetween. one of said rollers being radially movable away from and toward the other of said rollers. said support comprising:

at least one hydraulic cylinder for each bearing block. mounted between the press frame and the side of the bearing block which is away from the roller gap; and hydraulic circuit connected to said cylinder; motor pump for supplying hydraulic fluid through said circuit to said cylinder. maximuiii-minimum pressure switch within said circuit for starting said motor pump when a predetermined minimum prcssure is reached in said circuit and for stopping said motor pump when a predetermined maximum pressure is reached in said circuit; a prcssurivcd hydraulic storage tank in said circuit.

and pressure-limiting \alvc connected to said hydraulic circuit for releasing sufficient amounts of hydraulic fluid from said circuit. when the pressure within said circuit exceeds a predetermined operating 6 pressure, to keep the pressure within said circuit at 3. A hydraulic support in accordance with claim 1 said predetermined operating pressure. wherein said predetermined minimum pressure is 2. A hydraulic support in accordance with claim I slightly lower than said predetermined operating presfurther including a safety valve connected to said hysure. draulic circuit. 5 

1. A hydraulic support for the bearing blocks of a movable roller in a roll press having a frame and two rollers having a gap therebetween, one of said rollers being radially movable away from and toward the other of said rollers, said support comprising: at least one hydraulic cylinder for each bearing block, mounted between the press frame and the side of the bearing block which is away from the roller gap; and a hydraulic circuit connected to said cylinder; a motor pump for supplying hydraulic fluid through said circuit to said cylinder; a maximum-minimum pressure switch within said circuit for starting said motor pump when a predetermined minimum pressure is reached in said circuit and for stopping said motor pump when a predetermined maximum pressure is reached in said circuit; a pressurized hydraulic storage tank in said circuit; and a pressure-limiting valve connected to said hydraulic circuit for releasing sufficient amounts of hydraulic fluid from said circuit, when the pressure within said circuit exceeds a predetermined operating pressure, to keep the pressure within said circuit at said predetermined operating pressure.
 2. A hydraulic support in accordance with claim 1 further including a safety valve connected to said hydraulic circuit.
 3. A hydraulic support in accordance with claim 1 wherein said predetermined minimum pressure is slightly lower than said predetermined operating pressure. 